Clinical experience has shown that transluminal angioplasty can be an effective non-surgical therapy for selected patients with obstructive atherosclerotic vascular disease. However, its mechanism of action and long term consequences are incompletely understood. To examine these factors, three experimental rabbit models of atherosclerosis will be created. In one third of the animals, lesions will be created in the aorta and iliac vessels by balloon de-endothialization followed by a high cholesterol diet. The remaining animals will have lesions created by continued endothelial damage from an indwelling catheter followed by a normal diet or a high cholesterol diet. These models result in atherosclertoic lesions that vary from a predominantly foam cell lesion to a predominantly fibrous lesion. Animals from each model will be entered into three studies: An acute phase study will examine the angiographic, morphologic and biochemical changes that occur one day following angioplasty. The long term studies will focus on the progression of disease at the angioplasty site and the influence of dipyridamole and coumadin on this progression. The third phase will investigate the angiographic and histological effect of high frequency and ultrasonic vibration on the atherosclerotic plaque. The results of these studies should provide information about the mechanisms responsible for lumen enlargement following angioplasty and help define the factors responsible for its long term success. In understanding the effect of angioplasty and other forms of mechanical injury on atherosclerosis, further developments in the non-surgical treatment of atherosclerosis can be made.